Identification of Mycobacterium abscessus Subspecies by MALDI-TOF Mass Spectrometry and Machine Learning.

Mycobacterium abscessus is one of the most common and pathogenic nontuberculous mycobacteria (NTM) isolated in clinical laboratories. It consists of three subspecies: M. abscessus subsp. abscessus, M. abscessus subsp. bolletii, and M. abscessus subsp. massiliense. Due to their different antibiotic susceptibility pattern, a rapid and accurate identification method is necessary for their differentiation. Although matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) has proven useful for NTM identification, the differentiation of M. abscessus subspecies is challenging. In this study, a collection of 325 clinical isolates of M. abscessus was used for MALDI-TOF MS analysis and for the development of machine learning predictive models based on MALDI-TOF MS protein spectra. Overall, using a random forest model with several confidence criteria (samples by triplicate and similarity values >60%), a total of 96.5% of isolates were correctly identified at the subspecies level. Moreover, an improved model with Spanish isolates was able to identify 88.9% of strains collected in other countries. In addition, differences in culture media, colony morphology, and geographic origin of the strains were evaluated, showing that the latter had an impact on the protein spectra. Finally, after studying all protein peaks previously reported for this species, two novel peaks with potential for subspecies differentiation were found. Therefore, machine learning methodology has proven to be a promising approach for rapid and accurate identification of subspecies of M. abscessus using MALDI-TOF MS.

Clinical Evaluation of Nontuberculous Mycobacteria (NTM) Elite Agar, a New Medium for the Isolation of NTM: a Multicenter Study.

Nontuberculous mycobacteria (NTM) are gaining interest with the increased number of infected patients. NTM Elite agar is designed specifically for the isolation of NTM without the decontamination step. We assessed the clinical performance of this medium combined with Vitek mass spectrometry (MS) matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) technology for the isolation and identification of NTM in a prospective multicenter study, including 15 laboratories (24 hospitals). A total of 2,567 samples from patients with suspected NTM infection were analyzed (1,782 sputa, 434 bronchial aspirates, 200 bronchoalveolar lavage samples, 34 bronchial lavage samples, and 117 other samples). A total of 220 samples (8.6%) were positive with existing laboratory methods against 330 with NTM Elite agar (12.8%). Using the combination of both methods, 437 isolates of NTM were detected in 400 positive samples (15.6% of samples). In total, 140 samples of the standard procedures (SP) and 98 of the NTM Elite agar were contaminated. NTM Elite agar showed a higher performance for rapidly growing mycobacteria (RGM) species than SP (7% versus 3%, P < 0.001). A trend has been noted for the Mycobacterium avium complex (4% with SP versus 3% with NTM Elite agar, P = 0.06). The time to positivity was similar (P = 0.13) between groups. However, the time to positivity was significantly shorter for the RGM in subgroup analysis (7 days with NTM and 6 days with SP, P = 0.01). NTM Elite agar has been shown to be useful for the recovery of NTM species, especially for the RGM. Using NTM Elite agar + Vitek MS system in combination with SP increases the number of NTM isolated from clinical samples.

Antimicrobial susceptibility of 6 antimicrobial agents in Helicobacter pylori clinical isolates by using EUCAST breakpoints compared with previously used breakpoints.

INTRODUCTION: The aim of this study was to determine the differences in percentage resistance in H. pylori clinical isolates using EUCAST breakpoints compared with previously used breakpoints. MIC value distribution in H. pylori clinical isolates was also studied. METHODS: Susceptibility to amoxicillin, tetracycline, metronidazole, clarithromycin, rifampicin and levofloxacin was performed by E-test in 824 H. pylori clinical isolates. EUCAST and previous breakpoints defined resistance as follows: MIC >0.12mg/L and ≥2mg/L for amoxicillin, >8mg/L and ≥8mg/L for metronidazole, >0.5mg/L and ≥1mg/L for clarithromycin, >1mg/L and ≥32mg/L for rifampicin, and >1mg/L and ≥4mg/L for tetracycline and >1mg/L levofloxacin. RESULTS: Overall resistance rate by EUCAST and by previous breakpoints was 8.5% and 3.2% for amoxicillin, 0.6% and 0.1% for tetracycline, 39.2% and 39.7% for metronidazole, 51.2% and 51.2% for clarithromycin, 32% and 3.1% for rifampicin, and 6.7% and 6.7% for levofloxacin. CONCLUSIONS: When using the different breakpoints for antimicrobial susceptibility testing, similar results were found with most antibiotics tested (tetracycline, metronidazole, clarithromycin, and levofloxacin), except for amoxicillin and rifampicin.

[Application of mass spectrometry in mycobacteria]. / Aplicación de la espectrometría de masas en micobacterias.

To date, more than 170 species of mycobacteria have been described, of which more than one third may be pathogenic to humans, representing a significant workload for microbiology laboratories. These species must be identified in clinical practice, which has long been a major problem due to the shortcomings of conventional (phenotypic) methods and the limitations and complexity of modern methods largely based on molecular biology techniques. The aim of this review was to briefly describe different aspects related to the use of MALDI-TOF (matrix-assisted laser desorption ionization time-of-flight) mass spectrometry (MS) for the identification of mycobacteria. Several difficulties are encountered with the use of this methodology in these microorganisms mainly due to the high pathogenicity of some mycobacteria and the peculiar structure of their cell wall, requiring inactivation and special protein extraction protocols. We also analysed other relevant aspects such as culture media, the reference methods employed (gold standard) in the final identification of the different species, the cut-off used to accept data as valid, and the databases of the different mass spectrometry systems available. MS has revolutionized diagnosis in modern microbiology; however, specific improvements are needed to consolidate the use of this technology in mycobacteriology.

Microevolution, reinfection and highly complex genomic diversity in patients with sequential isolates of Mycobacterium abscessus.

Mycobacterium abscessus is an opportunistic, extensively drug-resistant non-tuberculous mycobacterium. Few genomic studies consider its diversity in persistent infections. Our aim was to characterize microevolution/reinfection events in persistent infections. Fifty-three sequential isolates from 14 patients were sequenced to determine SNV-based distances, assign resistance mutations and characterize plasmids. Genomic analysis revealed 12 persistent cases (0-13 differential SNVs), one reinfection (15,956 SNVs) and one very complex case (23 sequential isolates over 192 months), in which a first period of persistence (58 months) involving the same genotype 1 was followed by identification of a genotype 2 (76 SNVs) in 6 additional alternating isolates; additionally, ten transient genotypes (88-243 SNVs) were found. A macrolide resistance mutation was identified from the second isolate. Despite high diversity, the genotypes shared a common phylogenetic ancestor and some coexisted in the same specimens. Genomic analysis is required to access the true intra-patient complexity behind persistent infections involving M. abscessus.

The geographic diversity of nontuberculous mycobacteria isolated from pulmonary samples: an NTM-NET collaborative study.

A significant knowledge gap exists concerning the geographical distribution of nontuberculous mycobacteria (NTM) isolation worldwide. To provide a snapshot of NTM species distribution, global partners in the NTM-Network European Trials Group (NET) framework (www.ntm-net.org), a branch of the Tuberculosis Network European Trials Group (TB-NET), provided identification results of the total number of patients in 2008 in whom NTM were isolated from pulmonary samples. From these data, we visualised the relative distribution of the different NTM found per continent and per country. We received species identification data for 20 182 patients, from 62 laboratories in 30 countries across six continents. 91 different NTM species were isolated. Mycobacterium avium complex (MAC) bacteria predominated in most countries, followed by M. gordonae and M. xenopi. Important differences in geographical distribution of MAC species as well as M. xenopi, M. kansasii and rapid-growing mycobacteria were observed. This snapshot demonstrates that the species distribution among NTM isolates from pulmonary specimens in the year 2008 differed by continent and differed by country within these continents. These differences in species distribution may partly determine the frequency and manifestations of pulmonary NTM disease in each geographical location.

First report of a carbapenemase OXA-48-producing Hafnia alvei clinical isolate.

Introduction: Carbapenems are usually used in the treatment of infections caused by cephalosporin-resistant Enterobacterales ; however, the increase in carbapenem-resistant Enterobacterales (CRE) has become one of the most important problems in public health. Hafnia alvei is associated with intestinal and extraintestinal infections, especially in patients with any chronic disease or some type of immunosupression. H. alvei is resistant to first-generation aminopenicillins and cephalosporins owing to the ß-lactamase (Amp C) in their chromosome; the only carbapenem-resistant Hafnia strain described until now was due to a lack of the OmpK36 protein that plays an important role in permeability to carbapenems. Case presentation: We present the case of a 65-year-old male diagnosed with acute lithiasic cholecystitis. Culture of the biliary prosthesis yielded a OXA-48-producing H. alvei that was identified by MALDI-TOF (matrix-assisted laser desorption/ionization-time of flight) MS. Carbapenemase production was detected by immunochromatography and confirmed by sequencing. Conclusion: To our knowledge, this is the first report of OXA-48-producing H. alvei probably obtained by horizontal transfer from Enterobacter cloacae OXA-48 isolated in previous samples.

Subspecies Distribution and Antimicrobial Susceptibility Testing of Mycobacterium abscessus Clinical Isolates in Madrid, Spain: a Retrospective Multicenter Study.

Mycobacterium abscessus (MABS) is the most pathogenic and drug-resistant rapidly growing mycobacteria. However, studies on MABS epidemiology, especially those focusing on subspecies level, are scarce. We aimed to determine MABS subspecies distribution and its correlation with phenotypic and genotypic antibiotic profiles. A retrospective multicenter study of 96 clinical MABS isolates in Madrid between 2016 to 2021 was conducted. Identification at the subspecies level and resistance to macrolides and aminoglycosides were performed by the GenoType NTM-DR assay. The MICs of 11 antimicrobials tested against MABS isolates were determined using the broth microdilution method (RAPMYCOI Sensititer titration plates). Clinical isolates included 50 (52.1%) MABS subsp. abscessus; 33 (34.4%) MABS subsp. massiliense; and 13 (13.5%) MABS subsp. bolletii. The lowest resistance rates corresponded to amikacin (2.1%), linezolid (6.3%), cefoxitin (7.3%), and imipenem (14.6%), and the highest to doxycycline (100.0%), ciprofloxacin (89.6%), moxifloxacin (82.3%), cotrimoxazole (82.3%), tobramycin (81.3%), and clarithromycin (50.0% at day 14 of incubation). Regarding tigecycline, although there are no susceptibility breakpoints, all strains but one showed MICs ≤ 1 µg/mL. Four isolates harbored mutations at positions 2058/9 of the rrl gene, one strain harbored a mutation at position 1408 of the rrl gene, and 18/50 harbored the T28C substitution at erm(41) gene. Agreement of the GenoType results with clarithromycin and amikacin susceptibility testing was 99.0% (95/96). The rate of MABS isolates showed an upward trend during the study period, being M. abscessus subsp. abscessus the most frequently isolated subspecies. Amikacin, cefoxitin, linezolid, and imipenem showed great in vitro activity. The GenoType NTM-DR assay provides a reliable and complementary tool to broth microdilution for drug resistance detection. IMPORTANCE Infections caused by Mycobacterium abscessus (MABS) are increasingly being reported worldwide. Identifying MABS subspecies and assessing their phenotypic resistance profiles are crucial for optimal management and better patient outcomes. M. abscessus subspecies differ in erm(41) gene functionality, which is a critical determinant of macrolide resistance. Additionally, resistance profiles of MABS and the subspecies distribution can vary geographically, highlighting the importance of understanding local epidemiology and resistance patterns. This study provides valuable insights into the epidemiology and resistance patterns of MABS and its subspecies in Madrid. Elevated resistance rates were observed for several recommended antimicrobials, emphasizing the need for cautious drug use. Furthermore, we assessed the GenoType NTM-DR assay, which examines principal mutations in macrolides and aminoglycosides resistance-related genes. We observed a high level of agreement between the GenoType NTM-DR assay and the microdilution method, indicating its usefulness as an initial tool for early initiation of appropriate therapy.

Performance of Xpert MTB/RIF Ultra assay on respiratory and extra-respiratory samples in a high-resource setting with a low tuberculosis prevalence.

The Xpert MTB/RIF assay is a molecular assay that has improved the detection of tuberculosis and rifampicin resistance. However, its sensitivity is limited in patients with paucibacillary disease. Xpert MTB/RIF Ultra has been developed to resolve this limitation. We compared the performance of Xpert Ultra with that of culture for detection of Mycobacterium tuberculosis and rifampicin resistance. We reviewed laboratory records for 848 respiratory and 419 extrarespiratory samples that were processed between April 2018 and October 2019. The sensitivity, specificity, negative predictive value, and positive predictive value of Xpert Ultra were 94.8%, 98%, 98.8%, and 91.3% for respiratory samples and 83.8%, 96.9%, 98.4% and 72.1% for nonrespiratory ones. We found 26 culture-negative/Ultra-positive samples. Most of them have low bacillary burden and more than half belonged to patients with history of tuberculosis. Xpert Ultra demonstrates excellent diagnostic accuracy for tuberculosis detection, including paucibacillary specimens. In patients with history of tuberculosis, PCR results should be interpreted carefully.

Prevalence and importance of non-tuberculous mycobacteria in adult patients with cystic fibrosis in a hospital in Madrid. / Prevalencia e importancia de micobacterias no tuberculosas en pacientes adultos con fibrosis quística en un hospital de Madrid.

INTRODUCTION: The role of non-tuberculous mycobacteria (NTM) among cystic fibrosis (CF) patients, on occasion, remains unknown. The aim of our study is to evaluate the prevalence and clinical/microbiological characteristics of CF adult patients colonized by NTM, highlighting Mycobacterium abscessus (M. abscessus). METHODS: A retrospective study was conducted with 92 CF adult patients: including a control group of 64 patients, not colonized by NTM, and a study group of 28 patients, colonized by NTM. We have analyzed variables such as age, F508del mutation, lung function, pancreatic involvement, auramine staining and co-colonizations between both groups. RESULTS: The prevalence of NTM found was 30.4%. The most prevalent was Mycobacterium avium complex followed by M. abscessus. For M. abscessus, in the comparative study with patients colonized by other NTM, significant results were obtained for variables age. DISCUSSION: We have found a high prevalence of NTM among adult patients with CF, and we associated the presence of M. asbcessus with ages less than 30 years and F508del. Due to the pathogenic role of NTM, especially M. asbcessus, multicenter studies are required within the population suffering from CF.

Linezolid for therapy of Staphylococcus aureus meningitis: a cohort study of 26 patients.

BACKGROUND: Linezolid has good penetration to the meninges and could be an alternative for treatment of Staphylococcus aureus meningitis. We assessed the efficacy and safety of linezolid therapy for this infection. METHODS: Retrospective multicenter cohort study of 26 adults treated with linezolid, derived from a cohort of 350 cases of S. aureus meningitis diagnosed at 11 university hospitals in Spain (1981-2015). RESULTS: There were 15 males (58%) and mean age was 47.3 years. Meningitis was postoperative in 21 (81%) patients. The infection was nosocomial in 23 (88%) cases, and caused by methicillin-resistant S. aureus in 15 cases and methicillin-susceptible S. aureus in 11. Linezolid was given as empirical therapy in 10 cases, as directed therapy in 10, and due to failure of vancomycin in 6. Monotherapy was given to 16 (62%) patients. Median duration of linezolid therapy was 17 days (IQR 12-22 days) with a daily dose of 1,200 mg in all cases. The clinical response rate to linezolid was 69% (18/26) and microbiological response was observed in 14 of 15 cases evaluated (93%). Overall 30-day mortality was 23% and was directly associated with infection in most cases. When compared with the patients of the cohort, no significant difference in mortality was observed between patients receiving linezolid or vancomycin for therapy of methicillin-resistant S. aureus meningitis (9% vs. 20%; p = .16) nor between patients receiving linezolid or cloxacillin for therapy of methicillin-susceptible S. aureus meningitis (20% vs 14%; p = .68). Adverse events appeared in 14% (3/22) of patients, but linezolid was discontinued in only one patient. CONCLUSIONS: Linezolid appears to be effective and safe for therapy of S. aureus meningitis. Our findings showed that linezolid may be considered an adequate alternative to other antimicrobials in meningitis caused by S. aureus.

Genotypic and Phenotypic Characteristics of Staphylococcus aureus Prosthetic Joint Infections: Insight on the Pathogenesis and Prognosis of a Multicenter Prospective Cohort.

BACKGROUND: Staphylococcus aureus is the leading cause of prosthetic joint infection (PJI). Beyond the antibiogram, little attention has been paid to the influence of deep microbiological characteristics on patient prognosis. Our aim was to investigate whether microbiological genotypic and phenotypic features have a significant influence on infection pathogenesis and patient outcome. METHODS: A prospective multicenter study was performed, including all S. aureus PJIs (2016-2017). Clinical data and phenotypic (agr functionality, ß-hemolysis, biofilm formation) and genotypic characteristics of the strains were collected. Biofilm susceptibility to antimicrobials was investigated (minimal biofilm eradication concentration [MBEC] assay). RESULTS: Eighty-eight patients (39.8% men, age 74.7 ±â€…14.1 years) were included. Forty-five had early postoperative infections (EPIs), 21 had chronic infections (CPIs), and 19 had hematogenous infections (HIs). Twenty (22.7%) were caused by methicillin-resistant S. aureus. High genotypic diversity was observed, including 16 clonal complexes (CCs), with CC5 being the most frequent (30.7%). agr activity was greater in EPI than CPI (55.6% vs 28.6%; P = .041). Strains causing EPI were phenotypically and genotypically similar, regardless of symptom duration. Treatment failure (36.5%) occurred less frequently among cases treated with implant removal. In cases treated with debridement and implant retention, there were fewer failures among those who received combination therapy with rifampin. No genotypic or phenotypic characteristics predicted failure, except vancomycin minimal inhibitory concentration ≥1.5 mg/L (23.1% failure vs 3.4%; P = .044). MBEC50 was >128 mg/L for all antibiotics tested and showed no association with prognosis. CONCLUSIONS: S. aureus with different genotypic backgrounds is capable of causing PJI, showing slight differences in clinical presentation and pathogenesis. No major microbiological characteristics were observed to influence the outcome, including MBEC.

Inhibitory effect of Gram-negative and Gram-positive microorganisms against Helicobacter pylori clinical isolates.

OBJECTIVES: To determine the in vitro inhibitory effect of several Gram-negative and Gram-positive microorganisms against Helicobacter pylori clinical isolates. METHODS: The in vitro effect of 32 microorganisms against H. pylori clinical isolates was determined by a diffusion method. Time-kill assay was performed with two Staphylococcus spp. strains. RESULTS: Anti-H. pylori activity was detected with Saccharomyces cerevisiae, Bacillus spp., 1 Enterococcus faecium and 2 Lactobacillus spp. against 7, 11, 1, 5 and 6 H. pylori strains tested. All Staphylococcus spp. showed an anti-H. pylori effect: one Staphylococcus auricularis and two Staphylococcus epidermidis against all H. pylori tested; Staphylococcus aureus, Staphylococcus hominis and S. auricularis against six, five and seven H. pylori strains; and two other coagulase-negative Staphylococcus against one H. pylori strain. An inhibitory effect was detected with one Escherichia coli against one H. pylori. Klebsiella pneumoniae, Salmonella spp. and Acinetobacter baumannii showed activity against four H. pylori strains, and Enterobacter cloacae and Stenotrophomonas maltophilia showed activity against 14 H. pylori isolates. No anti-H. pylori activity was detected with one Lactobacillus spp., two Lactococcus lactis, four Streptococcus spp., one Bacillus cereus, one E. faecium, one Enterococcus faecalis, one E. coli, Pseudomonas aeruginosa and Klebsiella oxytoca. Time-kill assay showed bactericidal activity at 24 h with the two Staphylococcus spp. strains tested. CONCLUSIONS: Several strains of human pathogens or commensal bacteria are able to inhibit H. pylori growth in vitro and it is a strain-dependent phenomenon.

Detection of clarithromycin-resistant Helicobacter pylori in frozen gastric biopsies from pediatric patients by a commercially available fluorescent in situ hybridization.

Clarithromycin resistance is an important factor of eradication failure. A commercially available fluorescent in situ hybridization (FISH) kit (creaFAST) was used to detect H. pylori infection and the resistance to clarithromycin in frozen biopsies. A total of 33 biopsies, H. pylori culture-positive, obtained from pediatric patients were retrospectively studied. Clarithromycin resistance was compared with MICs detected by E-test from H. pylori clinical isolates. All culture-positive biopsies were positive by FISH. Detection of clarithromycin resistance showed sensitivity of 90%, specificity of 100%, positive predictive value of 100%, and negative predictive value of 86.7% compared with results obtained by E-test. Discrepant results were 2 biopsies, clarithromycin-susceptible by FISH but intermediate by E-test. In conclusion, FISH technology is a rapid, easy-to-implement, and reliable cultivation-independent method for routine application; however, when frozen biopsies are studied, some modification of the recommended procedure should be used to obtain better results.

[Cerebrospinal fluid shunt-associated meningitis caused by Gordonia sputi: case report and review of the literature].

We report the first known case of cerebrospinal fluid (CSF) shunt-associated meningitis caused by Gordonia sputi and review published cases of Gordonia CNS infections.

Peritonitis caused by Blastomonas natatoria in a patient submitted to peritoneal dyalisis / Blastomonas natatoria en un paciente sometido a diálisis peritoneal

No disponible

Derrame pleural tras tratamiento intravesical con bacilo de Calmette-Guérin / Pleural effusion after intravesical administration of bacillus Calmette-Guérin

No disponible

[Pneumococcal bacteremia in adult patients at a hospital in Madrid: serotypes and susceptibility]. / Bacteriemia neumocócica en pacientes adultos de un hospital de Madrid: serotipos y sensibilidad antibiótica.

INTRODUCTION: The aim of this study is to describe the distribution of Streptococcus pneumoniae serotypes, its antimicrobial susceptibility profiles and the relation with vaccines in pneumococcal invasive strains isolated from blood cultures of adult patients. METHODS: All pneumococci isolated (67 strains) from blood cultures were serotyped by latex agglutination (Pneumotest latex) and Quellung reaction (Statens Serum Institut, Denmark). Antimicrobial susceptibility testing to penicillin (PEN), cefotaxime (CT), erythromycin (ERY) and levofloxacin (LEV) was performed by the E-test method (Biomèrieux, France). RESULTS: Among the 67 strains isolated, the most prevalent serotypes were 22F (11.9%) and 3 (11.9%), the second most frequent were 7F (7.5%) and 19A (7.5%). The coverage of the strains by the pneumococcal 7-valent conjugate vaccine (VNC7V), pneumococcal 13-valent conjugate vaccine (VNC13V) and pneumococcal 23-valent polysaccharide (VNP23V) were 16, 49 and 82%, respectively. Serotypes 22F and 3 were responsible for 14 of the 48 episodes of pneumonia with bacteremia (29.2%) and only 2 of the 19 episodes (10.5%) of bacteremia without pneumonia. According to the 2007 CLSI criteria, 12 strains (17.9%) were non-susceptible to penicillin. Eleven of this 12 strains (91.7%) were resistant to erythromycin, simultaneously. CONCLUSIONS: The most common serotypes were 22F, 3, 7F y 19A. Three of them (3, 7F y 19A) are serotypes that are covered by the new VNC13V but not by VNC7V. Serotype 22F is a serotype emergent that is not covered by the VNC7V. The percentage of non-susceptibility to penicillin and resistance to erythromycin was comparable to the percentage reported in our country.

Antimicrobial susceptibility of 6 antimicrobial agents in Helicobacter pylori clinical isolates by using EUCAST breakpoints compared with previously used breakpoints / Sensibilidad de aislamientos clínicos de Helicobacter pylori a seis antimicrobianos utilizando los criterios EUCAST y comparando los resultados con criterios utilizados anteriormente

INTRODUCTION: The aim of this study was to determine the differences in percentage resistance in H. pylori clinical isolates using EUCAST breakpoints compared with previously used breakpoints. MIC value distribution in H. pylori clinical isolates was also studied. METHODS: Susceptibility to amoxicillin, tetracycline, metronidazole, clarithromycin, rifampicin and levofloxacin was performed by E-test in 824 H. pylori clinical isolates. EUCAST and previous breakpoints defined resistance as follows: MIC > 0.12 mg/L and ≥ 2 mg/L for amoxicillin, > 8 mg/L and ≥ 8 mg/L for metronidazole, > 0.5 mg/L and ≥ 1 mg/L for clarithromycin, >1mg/L and ≥ 32 mg/L for rifampicin, and > 1 mg/L and ≥ 4 mg/L for tetracycline and >1mg/L levofloxacin. RESULTS: Overall resistance rate by EUCAST and by previous breakpoints was 8.5% and 3.2% for amoxicillin, 0.6% and 0.1% for tetracycline, 39.2% and 39.7% for metronidazole, 51.2% and 51.2% for clarithromycin, 32% and 3.1% for rifampicin, and 6.7% and 6.7% for levofloxacin. CONCLUSIONS: When using the different breakpoints for antimicrobial susceptibility testing, similar results were found with most antibiotics tested (tetracycline, metronidazole, clarithromycin, and levofloxacin), except for amoxicillin and rifampicin

INTRODUCCIÓN: El objetivo de este estudio era determinar las diferencias en el porcentaje de resistencia de aislamientos clínicos de H. pylori usando los puntos de corte de EUCAST comparado con los puntos de corte usados anteriormente. También se estudió la distribución de los valores de CMI en los aislamientos de H. pylori. MÉTODOS: La sensibilidad de amoxicilina, tetraciclina, metronidazol, claritromicina, rifampicina y levo-floxacina se determinó mediante E-test en 824 aislamientos clínicos de H. pylori. Los puntos de corte utilizados fueron EUCAST: CMI > 0,12 mg/L para amoxicilina, > 8 mg/L para metronidazol, >0,5mg/L para claritromicina y > 1 mg/L para rifampicina, tetraciclina y levofloxacina. Los puntos de corte que se habían utilizado antes de EUCAST fueron: CMI ≥ 2 mg/L para amoxicilina, ≥ 8 mg/L para metronidazol, ≥ 1 mg/L para claritromicina, ≥ 32 mg/L para rifampicina, ≥ 4 mg/L para tetraciclina y > 1 mg/L para levofloxacina. RESULTADOS: La resistencia global con los puntos de corte EUCAST y con los puntos de corte anteriores fue: 8,5% y 3,2% para amoxicilina, 0,6% y 0,1% para tetraciclina, 39,2% y 39,7% para metronidazol, 51,2% y 51,2% para claritromicina, 32% y 3,1% para rifampicina y 6,7% y 6,7% para levofloxacina. CONCLUSIÓN: A pesar de la utilización de diferentes puntos de corte, se obtuvieron resultados de resistencia similares para la mayoría de los antibióticos probados (tetraciclina, metronidazol, claritrnnñomicina, y levofloxacino), con la única excepción de amoxicilina y rifampicina